Metal coating removing apparatus and metal coating removing method

ABSTRACT

A metal coating removing apparatus ( 1 ) includes a first electrode ( 13 ) arranged so as to be opposed to a metal coating ( 101 ) as an object to be removed, a second electrode  14  arranged so as to be opposed to the metal coating ( 101 ) at a predetermined distance from the first electrode ( 13 ), and a pulse power generator ( 11 ), for example, that functions as a discharge energy supply portion. The pulse power generator ( 11 ) supplies discharge energy between the first electrode ( 13 ) and the second electrode ( 14 ) so as to allow discharging to occur between the first electrode ( 13 ) and the second electrode ( 14 ). By allowing discharging to occur between the first electrode ( 13 ) and the second electrode ( 14 ), the metal coating ( 101 ) can be removed.

TECHNICAL FIELD

The present invention relates to an apparatus and a method for removinga metal coating provided on a surface of a resin, and particularly to anapparatus and a method for removing a metal coating with a view torecycling resins.

BACKGROUND ART

In recent years, there is a demand for recycling resin products used inelectric equipment and the like for the purpose of recycling resources.A lot of resin products used in electric equipment have their surfacescovered with a metal coating, which has to be removed when recyclingresins.

Conventionally, it has been proposed to put a resin product with a metalcoating into hot water so as to heat the same, thereby removing themetal coating (see, for example, Patent document 1). More specifically,the resin product, whose metal coating provided on its surface is cutwith a cutter or the like previously, is heated in hot water with atemperature of 70° C. or higher for several hours, and then the metalcoating is removed with running water.

Further, the following method also has been proposed to recover resinsfrom a resin plate with a metal coating. That is, the resin plateprovided with the metal coating initially is rolled, then the rolledresin plate is brought into contact with hot water or steam so as toallow resins to swell, the resin plate is pressed further, and then themetal coating is removed with running heated water (see, for example,Patent document 2).

-   Patent document 1: JP 5(1993)-345321 A-   Patent document 2: International Publication No. 96/12598

However, although the above-mentioned conventional methods are capableof removing a metal coating with a relatively low adhesion strength,such as a vapor deposited film, it is difficult to remove a metalcoating with a large thickness and a high adhesion strength, such as aplating film for ornamental purposes. Moreover, since theabove-mentioned conventional methods include treatment with hot water,which makes resins swell, dehydration is required for recycling ofresins.

DISCLOSURE OF INVENTION

A metal coating removing apparatus according to the present inventionfor removing a metal coating provided on a surface of a resin, includes:a first electrode arranged so as to be opposed to an object to beremoved; a second electrode arranged so as to be opposed to the objectto be removed at a predetermined distance from the first electrode; anda discharge energy supply portion for supplying discharge energy betweenthe first electrode and the second electrode so as to allow dischargingto occur between the first electrode and the second electrode.

A metal coating removing method according to the present invention forremoving a metal coating provided on a surface of a resin, includes:arranging a first electrode and a second electrode so that they areopposed to an object to be removed; and supplying discharge energybetween the first electrode and the second electrode so as to allowdischarging to occur between the first electrode and the secondelectrode, thereby removing the object to be removed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a configuration of a metal coatingremoving apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a view showing a schematic configuration of the metal coatingremoving apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing the configuration of the metal coatingremoving apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a flow chart showing an operation of the metal coatingremoving apparatus according to Embodiment 1 of the present invention.

FIG. 5 is a circuit diagram showing an exemplary configuration of apulse power generator.

FIG. 6 is a circuit diagram showing another exemplary configuration ofthe pulse power generator.

FIG. 7 is a perspective view showing a configuration of a metal coatingremoving apparatus according to Embodiment 2 of the present invention.

FIG. 8 is a view showing a schematic configuration of the metal coatingremoving apparatus according to Embodiment 2 of the present invention.

FIG. 9 is a block diagram showing the configuration of the metal coatingremoving apparatus according to Embodiment 2 of the present invention.

FIG. 10 is a flow chart showing an operation of the metal coatingremoving apparatus according to Embodiment 2 of the present invention.

FIG. 11 is a perspective view showing a configuration of a metal coatingremoving apparatus according to Embodiment 3 of the present invention.

FIG. 12 is a view showing a schematic configuration of the metal coatingremoving apparatus according to Embodiment 3 of the present invention.

FIG. 13 is a perspective view showing in detail a mechanism forcontrolling electrodes of the metal coating removing apparatus accordingto Embodiment 3 of the present invention.

FIGS. 14A to 14D are views specifically illustrating states where adistance between the electrodes and an angle of the electrodes areadjusted.

FIG. 15 is a block diagram showing the configuration of the metalcoating removing apparatus according to Embodiment 3 of the presentinvention.

FIG. 16 is a flow chart showing an operation of the metal coatingremoving apparatus according to Embodiment 3 of the present invention.

FIG. 17 is a perspective view showing a configuration in which a gasinjection portion is provided additionally at an insulating cover.

FIG. 18 is a cross-sectional view showing an exemplary positionalrelationship between the electrode and the insulating cover.

FIG. 19 is a perspective view showing a configuration of a metal coatingremoving apparatus according to Embodiment 4 of the present invention.

FIG. 20A is a perspective view showing an example of an electrodeportion when preliminary discharging is performed by the metal coatingremoving apparatus shown in FIG. 19. FIG. 20B is a side viewcorresponding to FIG. 20A, which includes a cross section of theelectrode portion.

FIG. 21 is a block diagram showing the configuration of the metalcoating removing apparatus according to Embodiment 4 of the presentinvention.

FIG. 22 is a flow chart showing an operation of the metal coatingremoving apparatus according to Embodiment 4 of the present invention.

FIG. 23A is a perspective view showing another example of the electrodeportion when preliminary discharging is performed by the metal coatingremoving apparatus shown in FIG. 19. FIG. 23B is a side viewcorresponding to FIG. 23A, which includes a cross section of theelectrode portion.

FIG. 24 is a partially cross-sectional schematic view showing anotherexemplary configuration of electrodes.

FIG. 25 is a partially cross-sectional schematic view showing anotherexemplary configuration of the electrodes.

FIGS. 26A and 26B are partially cross-sectional schematic views of theelectrodes having the configuration shown in FIG. 25, FIG. 26A showing astate of the electrodes during a removal operation and FIG. 26B showinga state of the electrodes during preliminary discharging.

FIG. 27 is a block diagram showing a configuration of a metal coatingremoving apparatus according to Embodiment 5 of the present invention.

FIG. 28 is a flow chart showing an operation of the metal coatingremoving apparatus according to Embodiment 5 of the present invention.

FIG. 29 is a partially cross-sectional schematic view showing anexemplary configuration of electrodes according to Embodiment 6 of thepresent invention.

FIG. 30A is a partially cross-sectional schematic view showing anotherexemplary configuration of the electrodes according to Embodiment 6 ofthe present invention. FIG. 30B is a cross-sectional view taken along aline I-I in FIG. 30A.

FIG. 31A is a perspective view showing still another exemplaryconfiguration of the electrodes according to Embodiment 6 of the presentinvention. FIG. 31B is a side view corresponding to FIG. 31A, whichincludes a cross section of an electrode portion.

FIG. 32 is a view for explaining an arrangement of electrodes accordingto examples of the present invention.

FIG. 33 is a graph showing the relationship between anelectrode-to-object to be removed distance and a removal area in thecase where an insulating cover is provided and in the case where aninsulating cover is not provided.

FIG. 34 is a graph showing the relationship between an applied voltageand the removal efficiency in the case where preliminary discharging isperformed and in the case where preliminary discharging is notperformed.

FIG. 35 is a graph showing the relationship between a gap and theremoval efficiency in the case where preliminary discharging isperformed and in the case where preliminary discharging is notperformed.

DESCRIPTION OF THE INVENTION

A metal coating removing apparatus according to the present inventionallows discharging to occur between a first electrode and a secondelectrode arranged so as to be opposed to a metal coating as an objectto be removed, thereby removing the metal coating provided on a surfaceof a resin. Therefore, even when the object to be removed is a metalcoating with a high adhesion strength or with a large thickness, it ispossible to remove the object to be removed from the resin efficiently.Further, the resin does not swell during a metal coating removaloperation, and therefore this apparatus can be used suitably with a viewto recycling resins.

Preferably, in the metal coating removing apparatus according to thepresent invention, at least one of the first electrode and the secondelectrode is covered with an insulating cover made of an insulatingmaterial except for at least a portion opposed to the object to beremoved. This allows discharging to occur in a predetermined space, sothat increased impact energy can be applied to the object to be removedby discharging. Accordingly, with an increase in impact energy, aremoval area of the object to be removed becomes larger, resulting in anincrease in removal efficiency. Further, the insulating cover and theelectrode covered with the insulating cover may be provided so thatrelative positions of the insulating cover and the electrode areadjustable. Further, the insulating cover is provided so that one end ofthe insulating cover contacts with the object to be removed during aremoval operation, and the electrode covered with the insulating covermay be provided so as to be kept from contact with the object to beremoved during the removal operation.

The metal coating removing apparatus according to the present inventionfurther may include an output control portion for controlling thedischarge energy supply portion, wherein the output control portioncontrols at least either one of an amount of the discharge energy and adischarge frequency supplied from the discharge energy supply portion.This allows discharging to occur in accordance with the thickness or thetype of a metal of the object to be removed, resulting in efficientremoval.

The metal coating removing apparatus according to the preset inventionfurther may include an electrode-to-electrode distance control portionfor controlling a distance between the first electrode and the secondelectrode. This makes it possible to select the distance between theelectrodes in accordance with the thickness or the type of a metal ofthe object to be removed, resulting in efficient removal.

The metal coating removing apparatus according to the present inventionfurther may include an electrode-to-object to be removed distancecontrol portion for controlling a distance between the first electrodeas well as the second electrode and the object to be removed. This makesit possible to select the distance between the electrodes and the objectto be removed in accordance with the thickness or the type of a metal ofthe object to be removed, resulting in efficient removal.

The metal coating removing apparatus according to the present inventionfurther may include an electrode angle control portion for controllingan angle of the first electrode and the second electrode with respect tothe object to be removed in a range of 0 to 90 degrees. This makes itpossible to select the angle of the electrodes in accordance with thethickness or the type of a metal of the object to be removed, resultingin efficient removal.

The metal coating removing apparatus according to the present inventionfurther may include an image recognition portion for recognizing a shapeof the object to be removed. This makes it possible to arrange theelectrodes and the like in accordance with the shape of the object to beremoved, resulting in efficient removal.

The metal coating removing apparatus according to the present inventionfurther may include a film thickness measurement portion for measuring athickness of the object to be removed. This makes it possible to changethe discharge energy and the like as appropriate in accordance with thefilm thickness of the object to be removed, and therefore efficientremoval can be achieved regardless of the film thickness of the objectto be removed.

The metal coating removing apparatus according to the present inventionfurther may include a metal recognition portion for recognizing a typeof a metal of the object to be removed. This makes it possible to changethe discharge energy and the like as appropriate in accordance with thetype of a metal of the object to be removed, and therefore efficientremoval can be achieved regardless of the type of a metal of the objectto be removed.

Preferably, in the metal coating removing apparatus according to thepresent invention, a distance between the first electrode and the secondelectrode is not less than 1 mm and not more than 20 mm. When thedistance between the electrodes is not less than 1 mm, a phenomenon inwhich a current flows only through the air between the first electrodeand the second electrode due to dielectric breakdown caused in the airbetween the electrodes can be suppressed. Therefore, a further increasein removal efficiency can be achieved. Further, when the distancebetween the electrodes is not more than 20 mm, a removal portion can beconnected reliably between the first electrode and the second electrode,and therefore it is possible to prevent the object to be removed frombeing left partially. Note here that the distance between the firstelectrode and the second electrode used herein is a distance betweenportions of the first electrode and the second electrode wheredischarging occurs. In the case of rod-shape electrodes, for example,this distance is a distance between front end portions of the electrodeswhere discharging occurs.

Preferably, in the metal coating removing apparatus according to thepresent invention, a distance between the first electrode as well as thesecond electrode and the object to be removed is not less than 0.1 mmand not more than 3.0 mm. By setting the distance between the electrodesand the object to be removed within this range, the metal coating can beremoved efficiently while burning and melting of the resin duringdischarging are suppressed. Note here that the distance between thefirst electrode as well as the second electrode and the object to beremoved used herein is a distance between portions of the firstelectrode as well as the second electrode where discharging occurs andthe object to be removed. In the case of rod-shape electrodes, forexample, this distance is a distance between front end portions of theelectrodes where discharging occurs and the object to be removed.

Preferably, in the metal coating removing apparatus according to thepresent invention, an angle (inclination angle of each of the firstelectrode and the second electrode with respect to a surface of theobject to be removed) of the first electrode and the second electrodewith respect to the object to be removed is not less than 15 degrees andnot more than 90 degrees. Most preferably, the angle of the electrodesis 45 degrees. The reason for this is that a larger removal area can beobtained.

The metal coating removing apparatus according to the present inventionfurther may include a plasma generation portion for generating plasmabetween the first electrode and the second electrode. The plasmageneration portion may supply discharge energy between the firstelectrode and the second electrode so as to allow discharging(preliminary discharging) to occur between the first electrode and thesecond electrode, thereby generating plasma. Preferably, the preliminarydischarging is performed in the vicinity of a conductive material. Byproviding this plasma generation portion, in the case, for example,where an insulating film is provided on a surface of the metal coatingas an object to be removed or where a conductive portion and aninsulating portion are mixed on a surface of the object to be removed,such as a printed board, the metal coating can be removed efficientlywithout applying a high voltage. The reason for this is as follows. Thatis, when an insulating portion is provided on a surface of the object tobe removed, a high dielectric breakdown voltage is required. However, bygenerating plasma between the electrodes, the dielectric breakdownvoltage can be reduced, and thus discharging can occur without applyinga high voltage. Further, when preliminary discharging is performed inthe vicinity of a conductive material, it is possible to generate plasmathat allows the plasma state to be maintained even when the distancebetween the electrodes is increased after the preliminary discharging.In order to maintain the plasma state, thermal plasma is generatedpreferably. To this end, it is preferable to use electrodes formed of amaterial with high electric resistance, so that the electrodes easilyliberate heat by application of a voltage during preliminarydischarging. For example, electrodes formed of a material containingtungsten or the like can be used suitably.

The metal coating removing apparatus according to the present inventionfurther may include an insulating member arranged between the firstelectrode and the second electrode. With this configuration, theinsulating member limits a discharge space during discharging for theremoval of the coating, and therefore the metal coating can be removedefficiently.

The metal coating removing apparatus according to the present inventionmay include an insulating cap for covering front end portions of thefirst electrode and the second electrode. The insulating cap limits adischarge space, and therefore the metal coating can be removedefficiently.

A metal coating removing method according to the present inventionallows discharging to occur between a first electrode and a secondelectrode arranged so as to be opposed to a metal coating as an objectto be removed, thereby removing the metal coating provided on a surfaceof a resin. Therefore, even when the object to be removed is a metalcoating with a high adhesion strength or with a large thickness, it ispossible to remove the object to be removed. Further, the resin does notswell during a metal coating removal operation, and therefore thismethod can be used suitably with a view to recycling resins.

The metal coating removing method according to the present invention mayinclude controlling at least either one of an amount of the dischargeenergy and a discharge frequency in accordance with at least either oneof a thickness and a type of a metal of the object to be removed. Thismakes it possible to change the discharge energy and the like asappropriate in accordance with the thickness or the type of the objectto be removed, and therefore efficient removal can be achievedregardless of the thickness or the type of the object to be removed.

The metal coating removing method according to the present invention mayinclude controlling a distance between the first electrode and thesecond electrode in accordance with at least either one of a thicknessand a type of a metal of the object to be removed. This makes itpossible to change the distance between the electrodes as appropriate inaccordance with the thickness or the type of the object to be removed,and therefore efficient removal can be achieved regardless of thethickness or the type of the object to be removed.

The metal coating removing method according to the present invention mayinclude controlling a distance between the first electrode as well asthe second electrode and the object to be removed in accordance with atleast either one of a thickness and a type of a metal of the object tobe removed. This makes it possible to change the distance between theelectrodes and the object to be removed as appropriate in accordancewith the thickness or the type of the object to be removed, andtherefore efficient removal can be achieved regardless of the thicknessor the type of the object to be removed.

The metal coating removing method according to the present invention mayinclude controlling an angle of the first electrode and the secondelectrode with respect to the object to be removed in accordance with atleast either one of a thickness and a type of a metal of the object tobe removed. This makes it possible to change the angle of the electrodesas appropriate in accordance with the thickness or the type of theobject to be removed, and therefore efficient removal can be achievedregardless of the thickness or the type of the object to be removed.

The metal coating removing method according to the present invention mayinclude: subjecting the object to be removed to test removal ahead oftime; measuring a removal area obtained by the test removal; andcontrolling at least either one of an amount of the discharge energy anda discharge frequency in accordance with a result of measuring theremoval area. This makes it possible to set an appropriate dischargeenergy and the like in accordance with the object to be removed, andtherefore efficient removal can be achieved regardless of the thicknessor the type of the object to be removed.

The metal coating removing method according to the present invention mayinclude generating plasma between the first electrode and the secondelectrode before arranging the first electrode and the second electrodeso that they are opposed to the object to be removed. The plasma can begenerated by, for example, supplying discharge energy between the firstelectrode and the second electrode so as to allow preliminarydischarging to occur between the first electrode and the secondelectrode. Preferably, the preliminary discharging is performed in astate where, for example, the first electrode and the second electrodeare arranged in the vicinity of a conductive material. When preliminarydischarging is performed in the vicinity of a conductive material,plasma can be generated easily. By generating plasma ahead of timebetween the electrodes, in the case, for example, where an insulatingfilm is provided on a surface of the metal coating as an object to beremoved or where a conductive portion and an insulating portion aremixed on a surface of the object to be removed, such as a printed board,the metal coating can be removed efficiently without applying a highvoltage.

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings.

Embodiment 1

An embodiment of an apparatus and a method for removing a metal coatingaccording to the present invention will be described with reference toFIGS. 1 to 6.

FIGS. 1 and 2 show a state where a metal coating (object to be removed)101 provided on a surface of a resin 102 is removed by using a metalcoating removing apparatus 1 of the present embodiment. FIG. 1 is aperspective view of the metal coating removing apparatus 1, and FIG. 2is a view showing a schematic configuration of the metal coatingremoving apparatus 1. The metal coating removing apparatus 1 includes apulse power generator (discharge energy supply portion) 11, an outputcontrol device (output control portion) 12, a first electrode 13 and asecond electrode 14 as discharging electrodes, an insulating cover 15for covering each of the first electrode 13 and the second electrode 14,and a control unit 16. The metal coating removing apparatus 1 furtherincludes an image recognition device (image recognition portion) 17 forrecognizing the shape of the resin 102 and the metal coating 101. Thetype of the resin 102 and the metal coating 101 as an object to beremoved is not particularly limited. In FIG. 2, reference numeral 103denotes a place where the metal coating is removed.

The pulse power generator 11 includes a power source (herein, a directcurrent power source) and a pulse discharge circuit (including, forexample, a capacitor, a coil, and the like), and supplies dischargeenergy (apply a voltage) between the first electrode 13 and the secondelectrode 14, thereby allowing discharging to occur between the firstelectrode 13 and the second electrode 14. Herein, a pulse power ishigh-density energy concentrated in a small space in a short time (aboutμsec to nsec) by compressing stored energy in terms of time and space. Aspecific exemplary configuration of the pulse power generator 11 will bedescribed later.

The output control device 12 controls the magnitude of the dischargeenergy (energy amount) and the frequency (discharge frequency) outputfrom the pulse power generator 11 in accordance with the type of themetal coating 101, the thickness of the metal coating 101, and the like.

The first electrode 13 and the second electrode 14 have a rod shape, forexample, and are arranged at a predetermined distance from each other.In order for discharging to occur, the first electrode 13 is suppliedwith a high electric potential, and the second electrode 14 is suppliedwith a ground potential, whereby discharging occurs between theseelectrodes. Preferably, the first electrode 13 and the second electrode14 are formed of, for example, tungsten, a silver-tungsten alloy, acopper-tungsten alloy, or the like because these metals are consumedless after discharging. Further, preferably, the first electrode 13 andthe second electrode 14 have as sharp a front end as possible so as toallow discharging to occur easily. Further, a distance between the firstelectrode 13 and the second electrode 14 is preferably 1 mm or more, andmore preferably 1 mm to 20 mm in order to remove the object to beremoved completely between the first electrode 13 and the secondelectrode 14. By setting the distance between the electrodes in thismanner, discharging can occur efficiently, and it is possible to preventa phenomenon in which no current flows through the metal coating 101because of discharging occurring only between the electrodes, wherebythe metal coating 101 can be removed efficiently. Further, a distance(gap) between the first electrode 13 as well as the second electrode 14and the metal coating 101 is preferably 0.1 mm to 3.0 mm, and morepreferably 0.1 mm to 1.0 mm. By setting the distance between theelectrodes 13 and 14 and the metal coating 101 in this range, the resin102 is prevented from being burned during discharging, and the metalcoating 101 can be removed efficiently. When the electrodes 13 and 14contact with the metal coating 101 directly, the resin 102 may beburned. For this reason, preferably, the electrodes 13 and 14 are keptfrom contact with the metal coating 101 as much as possible. Forexample, a structure as shown in FIG. 18 is also available, in which afront end of the insulating covers 15 is located closer to the metalcoating 101 as an object to be removed than the front end of theelectrodes 13 and 14, so that a space 31 is provided between theelectrodes 13 and 14 and the metal coating 101, while the insulatingcovers 15 may contact with the metal coating 101 during discharging.When the electrodes 13 and 14 are kept from contact with the metalcoating 101 in this manner, even if the insulating covers 15 contactwith the metal coating 101, the resin 102 is less burned duringdischarging, and it is possible to suppress melting of the resin by heatgenerated by the electrodes 13 and 14 immediately after the discharging.Further, the position of the insulating covers 15 may be adjustablerelative to that of the electrodes 13 and 14.

The insulating cover 15 covers each of he first electrode 13 and thesecond electrode 14, and is provided so that at least one end (portionopposed to the metal coating 101) of each of the first electrode 13 andthe second electrode 14 is exposed. By attaching the insulating cover 15to each of the electrodes 13 and 14 in this manner, a space where apulse power is supplied is compressed, resulting in an increase inremoval efficiency. Preferably, the insulating cover 15 has high heatresistance because it has to withstand continuous discharging. On thisaccount, an insulating material with high thermal conductivity, such asaluminum oxide, silicon nitride, diamond, or the like is used preferablyas a material of the insulating cover 15.

The control unit 16 instructs the pulse power generator 11 to startdischarging, controls the output control device 12 in accordance withinformation from the image recognition device 17, and the like.

Hereinafter, a processing operation of the metal coating removingapparatus 1 will be described with reference to FIGS. 3 and 4. FIG. 3 isa block diagram showing the configuration of the metal coating removingapparatus 1, and FIG. 4 is a flow chart showing the operation of themetal coating removing apparatus 1.

When the image recognition device 17 confirms the metal coating 101 asan object to be removed, the control unit 16 recognizes (stores) theshape of the object to be removed and, upon receipt of this information,turns on a direct current power source 11 a of the pulse power generator11 (Step (hereinafter, abbreviated as S) 41, S42, and S43).

Then, test removal is performed so as to determine the voltage to beapplied (energy amount) and the discharge frequency. More specifically,the control unit 16 changes the mode of the output control device 12 toa 1-pulse mode (S44), and instructs the pulse power generator 11 toperform 1-pulse discharging with an applied voltage of 5 kV with respectto the object to be removed (S45). An area where the object was removedby the 1-pulse discharging is measured by the image recognition device17 (S46). The control unit 16 compares the information on the removalarea from the image recognition device 17 with data in a removal areadatabase 16 a, so as to judge whether or not an initialized voltage tobe applied (herein, 5 kV, for example) and an initialized dischargefrequency (herein, 100 Hz, for example) are appropriate (S47). If it isjudged that the initialized voltage to be applied and the initializeddischarge frequency are not appropriate, they are changed so as to besuitable for the object to be removed (S48 and S49). After the testremoval, the control unit 16 changes the mode of the output control unit12 from the 1-pulse mode to a continuous discharge mode.

After the voltage to be applied and the discharge frequency are judgedas being appropriate in S47 or after the values of the voltage to beapplied and the discharge frequency are changed appropriately in S48 andS49, respectively, the control unit 16 performs an operation to obtainan operational method suitable for the shape of the object to beremoved, and issues the instruction to a robot control device (not shownin FIGS. 1 and 2) 18 based on the result of the operation (S50).

The robot control device 18 is operated so as to move each of the firstelectrode 13 and the second electrode 14 to a predetermined position(S51). Then, the output control device 12 is operated to issue aninstruction concerning the voltage to be applied and the dischargefrequency to the pulse power generator 11, thereby preparing fordischarging (S52). The pulse power generator 11 starts discharging basedon the data from the output control device 12 (S53).

When the removal is completed, discharging is stopped so as to finishremoving the coating (S54). Thereafter, the robot control device 18 isoperated so as to return the first electrode 13 and the second electrode14 to their points of origin (S55), the voltage to be applied and thedischarge frequency of the output control device 12 are set to theirinitial values (voltage to be applied: 5 kV, discharge frequency: 100Hz), and the metal coating removal operation is finished.

Next, a description will be given of the data stored in the removal areadatabase 16 a. The removal area obtained by 1-pulse discharging variesdepending upon the applied voltage, the film thickness of the object tobe removed, and the type of the object to be removed as shown inTable 1. Thus, the relationship between a removal area during testrecording and an appropriate voltage to be applied as well as anappropriate discharge frequency in accordance with the removal areaduring the test recording is obtained previously, and these data arerecorded in the removal area database 16 a. Based on the removal areaobtained as a result of the test removal, an applied voltage suitablefor the object to be removed is obtained, and further a suitabledischarge frequency is determined from the removal area database 16 a.For example, in the case of a nickel-chromium plating film having athickness of 30 μm shown in Table 1, the removal area per 1 pulse is 0225 mm² even when the applied voltage is set as high as 20 kV. Thus, theremoval area is smaller in this case than in the case where a shieldplating film having a thickness of 1.25 μm is removed with an appliedvoltage of 5 kV. Consequently, the discharge frequency is required to beset higher than that for the shield plating film. Note here that inTable 1 the shield plating film is a metal coating having a two-layerstructure of copper (lower layer) and nickel (upper layer), and thenickel-chromium plating film is a metal coating having a three-layerstructure of copper (lower layer), nickel (middle layer), and chromium(upper layer).

TABLE 1 (Capacity of capacitor: 16 nF) Removal area (mm²) Film 5 kV 10kV 15 kV 20 kV thickness (0.2 J/ (0.8 J/ (1.8 J/ (3.2 Metal coating (μm)pulse) pulse) pulse) J/pulse) Shield plating film 1.25 0.666 2.202 3.8004.959 Nickel-chromium 30 0.019 0.067 0.310 0.225 plating film

Next, a specific example of the pulse power generator 11 will bedescribed with reference to FIGS. 5 and 6.

FIG. 5 shows an exemplary configuration of the pulse discharge circuitof the pulse power generator 11. In the exemplary configuration shown inFIG. 5, the pulse power generator 11 includes a primary-side circuit anda secondary-side circuit. In the pulse power generator 11 having such aconfiguration, when a direct current power source 111 is turned on bythe instruction from the control unit 16, a capacitor 112 of theprimary-side circuit starts being charged. The output control device 12determines the discharge frequency, and generates a TTL signal, therebyturning on a switch 113 (e.g., a thyristor). While the switch 113 isopened for a predetermined period of time, a current flowsinstantaneously by the electric charge held by the capacitor 112. Sincean inverse current flows from the capacitor 112 thereafter, a diode 114is connected in parallel with the switch 113. When a transformer 115 ispressurized, a capacitor 116 of the secondary circuit is charged (energyis transferred to the capacitor 116). A magnetic switch 117 iscontrolled by a voltage and a time. Until a voltage applied to themagnetic switch 117 reaches a predetermined level and a predeterminedperiod of time has elapsed, no voltage is applied to the first electrode13, so that no discharging occurs. When the voltage applied to themagnetic switch 117 reaches a predetermined level and a predeterminedperiod of time has elapsed, the magnetic switch 117 is turned on, sothat a current flows through the first electrode 13, and a pulse poweris applied to a surface of the metal coating 101, whereby the metalcoating 101 is removed.

FIG. 6 shows another exemplary configuration of the pulse dischargecircuit of the pulse power generator 11. In this configuration, when adirect current power source 118 is turned on by the instruction from thecontrol unit 16, a capacitor 119 starts being charged. The outputcontrol device 12 determines the discharge frequency, and generates aTTL signal, thereby turning on a switch 120. While the switch 120 isopened for a predetermined period of time, a current flowsinstantaneously by the electric charge held by the capacitor 119. Sincean inverse current flows from the capacitor 119 thereafter, a diode 121is connected in parallel with the switch 120. A current flows throughthe first electrode 13 from the capacitor 119, and a pulse power isapplied to a surface of the metal coating 101, whereby the metal coating101 is removed. In each of the exemplary configurations shown in FIGS. 5and 6, a higher reactance between the capacitor 116, 119 and the firstelectrode 13 results in a longer discharge time, and therefore,preferably, the reactance is reduced as much as possible so as tocompress energy in terms of time.

Embodiment 2

Another embodiment of an apparatus and a method for removing a metalcoating according to the present invention will be described withreference to FIGS. 7 to 10.

FIGS. 7 and 8 show a state where a metal coating 101 provided on asurface of a resin 102 is removed by using a metal coating removingapparatus 2 of the present embodiment. FIG. 7 is a perspective view ofthe metal coating removing apparatus 2, and FIG. 8 is a view showing aschematic configuration of the metal coating removing apparatus 2. Themetal coating removing apparatus 2 has the same configuration as that ofthe metal coating removing apparatus 1 of Embodiment 1 except that afilm thickness measuring device (film thickness measurement portion) 19,such as a fluorescent X-ray device, for measuring the thickness of themetal coating 101 as an object to be removed is provided further. Themetal coating removing apparatus 2 changes the magnitude of dischargeenergy (energy amount) and the frequency (discharge frequency) outputfrom a pulse power generator 11 in accordance with the thickness of theobject to be removed measured by the film thickness measuring device 19.The components common to those of the metal coating removing apparatus 1described in Embodiment 1 are denoted with the same reference numerals,and detailed descriptions thereof will be omitted here.

Hereinafter, a processing operation of the metal coating removingapparatus 2 will be described with reference to FIGS. 9 and 10. FIG. 9is a block diagram showing the configuration of the metal coatingremoving apapratus 2, and FIG. 10 is a flow chart showing the operationof the metal coating removing apparatus 2.

When an image recognition device 17 confirms the object to be removed, acontrol unit 16 recognizes the shape of the object to be removed, whichis performed in the same manner as for the metal coating removingapparatus 1 in Embodiment 1 (S41 and S42). However, the metal coatingremoving apparatus 2 determines the amount of the discharge energy andthe discharge frequency in a manner different from that of the metalcoating removing apparatus 1.

The metal coating removing apparatus 2 lowers, for example, a probe (notshown) for measuring a film thickness provided in the film thicknessmeasuring device 19 by using a motor or the like, for example, so as tomeasure the film thickness of the object to be removed (S110). Then,based on the result of measuring the film thickness, it is determinedwhether or not an initialized voltage to be applied and an initializeddischarge frequency are appropriate with respect to the film thicknessof the object to be removed. In the present embodiment, the initialvalue of the voltage to be applied is 5 kV, and the initial value of thedischarge frequency is 100 Hz. Thus, if the film thickness is smallerthan 10 μm, for example, as a result of the measurement, it is judgedthat the removal can be performed at the initial values. If the filmthickness is 10 μm or larger, it is judged that changes of the initialvalues are necessary (S102). If it is judged in S102 that changes of theinitial values are unnecessary, a direct current power source 11 a isswitched on. If it is judged in S102 that changes of the initial valuesare necessary, the control unit 16 compares the information on themeasured film thickness with data in a film thickness database 16 b, andchanges the initialized voltage to be applied and the initializeddischarge frequency into ones suitable for the film thickness of theobject to be removed (S103 and S104). According to this processing, anappropriate voltage to be applied and an appropriate discharge frequencycan be set in accordance with the film thickness of the object to beremoved, and therefore it is possible to remove the object to be removedstably even when it has a large film thickness.

The processing to be performed after determining the voltage to beapplied and the discharge frequency in accordance with the filmthickness of the object to be removed is the same as that in S50 to S56of the metal coating removing apparatus 1 described in Embodiment 1, anda description thereof will be omitted here.

Embodiment 3

Still another embodiment of an apparatus and a method for removing ametal coating according to the present invention will be described withreference to FIGS. 11 to 17.

FIGS. 11 and 12 show a state where a metal coating 101 provided on asurface of a resin 102 is removed by using a metal coating removingapparatus 3 of the present embodiment. FIG. 11 is a perspective view ofthe metal coating removing apparatus 3, and FIG. 12 is a view showing aschematic configuration of the metal coating removing apparatus 3. Themetal coating removing apparatus 3 has the same configuration as that ofthe metal coating removing apparatus 2 of Embodiment 2 except that amechanism 25 for controlling a first electrode 13 and a second electrode14 is provided. More specifically, the metal coating removing apparatus3 is different from the metal coating removing apparatus 2 in that adistance between the first electrode 13 and the second electrode 14 ismade variable, which can be controlled by an electrode-to-electrodedistance control portion, and that an angle of the first electrode 13and the second electrode 14 with respect to the object to be removed ismade variable, which can be controlled by an electrode angle controlportion. The components common to those of the metal coating removingapparatuses 1 and 2 are denoted with the same reference numerals, anddetailed descriptions thereof will be omitted here.

FIGS. 12 and 13 specifically show the mechanism for controlling thefirst electrode 13 and the second electrode 14. Each of the firstelectrode 13 and the second electrode 14 is covered with an insulatingcover 15, and is connected with an electrode angle adjusting motor 21via the insulating cover 15. In FIGS. 12 and 13, reference numeral 15 adenotes a ceramic tube constituting the insulating cover 15, which isformed integrally with a portion of the insulating cover 15 where theelectrode angle adjusting motor 21 is joined. The angle of the firstelectrode 13 and the second electrode 14 with respect to the object tobe removed can be adjusted by operating the electrode angle adjustingmotor 21. Further, each of the first electrode 13 and the secondelectrode 14 is joined to a rack gear 24 via the electrode angleadjusting motor 21, the rack gear 24 being moved linearly from side toside by the rotation of a pinion gear 23 (not shown in FIG. 12). Thepinion gear 23 is joined to an electrode-to-electrode distance adjustingmotor 22 and is rotated by operating the electrode-to-electrode distanceadjusting motor 22. The electrode angle adjusting motor 21 and theelectrode-to-electrode distance adjusting motor 22 are controlled by amotor control portion 20. The motor control portion 20 controls theelectrode angle adjusting motor 21 and the electrode-to-electrodedistance adjusting motor 22 upon receipt of a control signal from acontrol unit 16. Thus, in the present embodiment, theelectrode-to-electrode distance control portion is constituted by thecontrol unit 16, the motor control portion 20, theelectrode-to-electrode distance adjusting motor 22, the pinion gear 23,and the rack gear 24. The electrode angle control portion is constitutedby the control unit 16, the motor control portion 20, and the electrodeangle adjusting motor 21. FIGS. 14A to 14D show in detail states wherethe distance between the electrodes and the angle of the electrodes areadjusted.

Next, a processing operation of the metal coating removing apparatus 3will be described. The metal coating removing apparatus 3 is operated inthe same manner as for the metal coating removing apparatus 2 describedin Embodiment 2 except that the distance between the electrodes and theangle of the electrodes also are changed in accordance with thethickness of the object to be removed measured by a film thicknessmeasuring device 19. Hereinafter, the processing operation of the metalcoating removing apparatus 3 will be described with reference to FIGS.15 and 16. FIG. 15 is a block diagram showing the configuration of themetal coating removing apparatus 3, and FIG. 16 is a flow chart showingthe operation of the metal coating removing apparatus 3.

An image recognition device 17 confirms the object to be removed (S41),the control unit 16 recognizes the shape of the object to be removed(S42), and the film thickness is measured and the voltage to be appliedand the discharge frequency are changed (S10 to S104) in the same manneras for the metal coating removing apparatuses 1 and 2. The metal coatingremoving apparatus 3 further is capable of changing the distance betweenthe electrodes and the angle of the electrodes in accordance with thefilm thickness of the object to be removed (S161 and S162). According tothis processing, an appropriate distance between the electrodes and anappropriate angle of the electrodes can be set in accordance with thefilm thickness of the object to be removed, and therefore it is possibleto remove the object to be removed stably regardless of its filmthickness.

The processing to be performed after determining the voltage to beapplied and the discharge frequency in accordance with the filmthickness of the object to be removed is the same as that in S50 to S56of the metal coating removing apparatus 1 described in Embodiment 1, anda description thereof will be omitted here. Note here that the distancebetween the electrodes and the angle of the electrodes are returned totheir initial values finally (herein, the distance between theelectrodes is 5 mm and the angle of the electrodes is 90°, for example)(S163).

Further, as shown in FIG. 17, the insulating cover 15 may be providedwith a gas injection portion 15 b that allows gas to be injected alongthe electrode, so that inert gas can be injected along the electrodes 13and 14. Inert gas injected along the electrodes 13 and 14 suppressescarbonization of the resin and oxide formation from components of themetal coating during discharging, resulting in an increase in resinrecycling rate and metal recycling rate. The configuration shown in FIG.17 allows inert gas to be injected partially to discharge portions.However, the same effect can be achieved by performing the removaloperation in a state where the entire metal coating removing apparatus 3is kept under vacuum.

Each of the above-described metal coating removing apparatuses 2 and 3according to Embodiments 2 and 3 has a configuration that allows thevoltage to be applied and the like to be changed only in accordance withthe film thickness of the object to be removed. However, a metalrecognition device (metal recognition portion) may be provided furtherfor recognizing a metal of the object to be removed, which allows thevoltage to be applied and the like to be determined also inconsideration of the type of the metal. Such a configuration enablesmore efficient removal of the metal coating. As the metal recognitiondevice, a device can be used that recognizes a metal by means of, forexample, emission spectrochemical analysis, fluorescent X-ray analysis,resistivity measurement, or the like. Further, the above-described metalcoating removing apparatus according to each of Embodiments 1 to 3 has aconfiguration in which the robot control device 18 is used to move theelectrodes 13 and 14 to predetermined positions set previously. However,a configuration may be provided further for controlling a distancebetween the electrodes and the object to be removed in accordance withthe film thickness of the object to be removed or the like, so that thedistance between the electrodes and the object to be removed can bechanged in accordance with the film thickness of the object to beremoved or the like.

Embodiment 4

Another embodiment of an apparatus and a method for removing a metalcoating according to the present invention will be described withreference to FIGS. 19 to 26.

FIG. 19 shows a state where a metal coating 101 provided on a surface ofa resin is removed by using a metal coating removing apparatus 4 of thepresent embodiment. FIG. 19 is a perspective view of the metal coatingremoving apparatus 4. The metal coating removing apparatus 4 has thesame configuration as that of the metal coating removing apparatus 2 ofEmbodiment 2 except that a configuration (plasma generation portion) forgenerating plasma between a first electrode 13 and a second electrode 14before a removal operation is provided and that the first electrode 13and the second electrode 14 are arranged so that a predetermineddistance (distance between the electrodes that allows plasma generation)is kept between front end portions of the electrodes. The metal coatingremoving apparatus 4 generates plasma ahead of time between the firstelectrode 13 and the second electrode 14, and removes the metal coating101 by using the first and second electrodes 13 and 14 with the plasmastate maintained therebetween. The components common to those of themetal coating removing apparatuses 1 to 3 described in Embodiment 1 to 3are denoted with the same reference numerals, and detailed descriptionsthereof will be omitted here.

The metal coating removing apparatus 4 has a configuration for allowingdischarging (preliminary discharging) to occur between the firstelectrode 13 and the second electrode 14 before discharging during aremoval operation, thereby generating plasma between the first electrode13 and the second electrode 14. More specifically, a conductive plate(conductive material) 41 is provided for preliminary discharging. Theelectrodes 13 and 14 are moved to the top of the conductive plate 41and, as shown in FIGS. 20A and 20B, discharge energy is supplied(voltage is applied) between the first electrode 13 and the secondelectrode 14 on top of the conductive plate 41 to allow preliminarydischarging to occur, so that thermal plasma is generated between thefirst electrode 13 and the second electrode 14. FIG. 20A is aperspective view of the electrodes during preliminary discharging, andFIG. 20B is a partially cross-sectional side view corresponding to FIG.20A. Thus, in the present embodiment, the plasma generation portion isconstituted by a pulse power generator 11 and the conductive plate 41.Thermal plasma is generated between the electrodes 13 and 14 thatliberate heat by application of a voltage, and the heat thus generatedallows the plasma state to be maintained until a removal operationwithout continuing to apply a voltage.

As described above, plasma is generated ahead of time between theelectrodes 13 and 14, and a removal operation is performed while theplasma state is maintained. Therefore, even in the case where aninsulating film is provided on a surface of the metal coating 101 as anobject to be removed, such as a CD-ROM (Compact Disk-Read Only Memory),for example, the metal coating 101 can be removed from a resin 102without increasing a voltage significantly. In the case where aninsulating film is provided on the surface of the metal coating 101, inorder to perform a removal operation without generating plasma betweenthe electrodes 13 and 14, it is necessary to apply a high voltage or tobring the electrodes 13 and 14 into contact with the insulating film onthe surface. A higher current value allows a larger removal area to beobtained. However, the current value decreases with an increase involtage, resulting in a reduction in energy efficiency. Further, whenthe electrodes 13 and 14 are brought into contact with the insulatingfilm on the surface, it becomes difficult to perform a removal operationwhile moving the electrodes 13 and 14, resulting in a decrease inworkability. For these reasons, in the case of an object to be removedwith an insulating film provided on its surface, the metal coatingremoving apparatus 4 as in the present embodiment is applied preferably.

Hereinafter, an exemplary processing operation of the metal coatingremoving apparatus 4 will be described specifically with reference toFIGS. 21 and 22. FIG. 21 is a block diagram of the metal coatingremoving apparatus 4, and FIG. 22 is a flow chart showing the operationof the metal coating removing apparatus 4. The following description isdirected to the case where an object to be removed is the metal coating101 with an insulating film provided on its surface.

When an image recognition device 17 confirms the object to be removed, acontrol unit 16 recognizes the shape of the object to be removed, whichis performed in the same manner as for the metal coating removingapparatuses 1 to 3 in Embodiments 1 to 3 (S41 and S42). However, themetal coating removing apparatus 4 then generates plasma between thefirst electrode 13 and the second electrode 14, which is a differencefrom the metal coating removing apparatuses 1 to 3.

The metal coating removing apparatus 4 lowers, for example, a probe (notshown) for measuring a film thickness provided in a film thicknessmeasuring device 19 by using a motor or the like, for example, so as tomeasure the thickness of the insulating film provided on the surface ofthe metal coating 101 (S221). Then, based on the result of measuring thefilm thickness, it is determined whether or not an initialized voltageto be applied and an initialized discharge frequency are appropriatewith respect to the film thickness of the insulating film. In thepresent embodiment, the initial value of the voltage to be applied is 5kV, and the initial value of the discharge frequency is 100 Hz. Thus, ifthe film thickness is smaller than 10 μm, for example, as a result ofthe measurement, it is judged that the removal can be performed at theinitial values. If the film thickness is 10 μm or larger, it is judgedthat changes of the initial values are necessary (S222). If it is judgedin S222 that changes of the initial values are unnecessary, a directcurrent power source 11 a is switched on. If it is judged in S222 thatchanges of the initial values are necessary, the control unit 16compares the information on the measured film thickness with data in aninsulating film thickness database 16 c, and changes the initializedvoltage to be applied and the initialized discharge frequency into onessuitable for the film thickness of the insulating film (S223 and S224).According to this processing, an appropriate voltage to be applied andan appropriate discharge frequency during preliminary discharging can beset in accordance with the film thickness of the insulating film, andtherefore a necessary plasma state can be created so as to remove theobject to be removed stably even when the insulating film has a largefilm thickness.

After the voltage to be applied and the discharge frequency are judgedas being appropriate in S222 or after the values of the voltage to beapplied and the discharge frequency are changed appropriately in S223and S224, respectively, the control unit 16 determines the electrodemovement speed for preliminary discharging based on the conditions suchas the voltage to be applied, the discharge frequency, the distancebetween the electrodes, and the like, and issues the instruction to arobot control device 18 (S225). Further, the control unit 16 performs anoperation to obtain an operational method suitable for the shape of theobject to be removed, and issues the instruction to the robot controldevice 18 (S226).

The robot control device 18 is operated so as to move the firstelectrode 13 and the second electrode 14 to the position of theconductive plate 41 (S227). Then, the output control device 12 isoperated to issue an instruction concerning the voltage to be appliedand the discharge frequency to the pulse power generator 11, therebypreparing for preliminary discharging. The pulse power generator 11starts preliminary discharging based on the data from the output controldevice 12 (S228 and S229).

When preliminary discharging is completed, a removal operation isstarted (S230). The removal operation is performed in the same manner asin S101 to S104 and S50 to S54 of the metal coating removing apparatus 2described in Embodiment 2, and thus a description thereof will beomitted here.

When the removal operation is completed, the electrodes 13 and 14 arereturned to their points of origin (S55), the voltage to be applied andthe discharge frequency of the output control device 12 are set to theirinitial values (voltage to be applied: 5 kV, discharge frequency: 100Hz) (S56), and the metal coating removal operation is finished.

As described above, by performing preliminary discharging on top of theconductive plate 41, it becomes easy to create and maintain a thermalplasma state. Further, as shown in FIGS. 23A and 23B, when preliminarydischarging is performed in a state where a conductive plate 42 issandwiched between the first electrode 13 and the second electrode 14,thermal plasma can be generated more easily. FIG. 23A is a perspectiveview of the electrodes during preliminary discharging, and FIG. 23B is apartially cross-sectional side view corresponding to FIG. 23A. In FIGS.23A and 23B, preliminary discharging is performed on top of theconductive plate 41 in the state where the conductive plate 42 issandwiched between the electrodes. However, preliminary discharging alsocan be performed in the state where the conductive plate 42 issandwiched between the electrodes instead of performing preliminarydischarging on top of the conductive plate 41.

When the first electrode 13 and the second electrode 14 are provided sothat a distance between the electrodes and an angle of the electrodesare variable as in the metal coating removing apparatus 3 described inEmbodiment 3, by driving an electrode angle adjusting motor 43 that canadjust the angle of the electrodes by a rotational movement, forexample, as shown in FIG. 24, the distance between the first electrode13 and the second electrode 14 can be made small during preliminarydischarging so that plasma develops easily, while the distance betweenthe first electrode 13 and the second electrode 14 can be made largeduring the removal operation so as to obtain a large removal area. Inthe case where the distance between the electrodes and the angle of theelectrodes are variable, the distance between the electrodes and theangle of the electrodes during the coating removal operation may bechanged in accordance with the object to be removed as in the metalcoating removing apparatus 3 described in Embodiment 3.

Further, as shown in FIG. 25, an insulating cover 15 may be provided sothat a part of a front end portion of each of the first electrode 13 andthe second electrode 14 is exposed. In such a case, preferably, thefirst electrode 13 and the second electrode 14 are provided rotatably sothat portions to be opposed to each other are variable. By providing thefirst and second electrodes 13 and 14 rotatably, the first electrode 13and the second electrode 14 can be rotated so that portions covered withthe insulating covers 5 are opposed to each other as shown in FIG. 26Aduring the removal operation, while exposed portions are opposed to eachother as shown in FIG. 26B during preliminary discharging. Consequently,the distance between the electrodes is made small during preliminarydischarging, so as to generate plasma easily. During the removaloperation, the distance between the electrodes is made large due to theexistence of the insulating covers 15, resulting in a larger removalarea.

In the present embodiment, preliminary discharging is performed on theconductive plate. However, this is not necessarily required. Preliminarydischarging may be performed under the condition that allows thermalplasma to be generated by adjusting the distance between the electrodesor the like.

Embodiment 5

Another embodiment of an apparatus and a method for removing a metalcoating according to the present invention will be described withreference to FIGS. 27 and 28.

The metal coating removing apparatus of the present embodiment has thesame configuration as that of the metal coating removing apparatus 4(see FIG. 19) described in Embodiment 4 except that a conductivitymeasuring device is connected with a probe, for example, for measuring afilm thickness provided in a film thickness measuring device 19, so asto measure the conductivity on a surface of an object to be removed. Thecomponents common to those of the metal coating removing apparatuses 1to 4 described in Embodiment 1 to 4 are denoted with the same referencenumerals, and detailed descriptions thereof will be omitted here.

As in Embodiment 4, the metal coating removing apparatus of the presentembodiment also has a configuration for allowing preliminary dischargingto occur between a first electrode 13 and a second electrode 14, therebygenerating plasma. However, the metal coating removing apparatus of thepresent embodiment has the configuration for measuring the conductivityon the surface of the object to be removed, which makes it possible todetermine the necessity of preliminary discharging in accordance withthe state of the surface of the object to be removed. Thus, this metalcoating removing apparatus also can be applied effectively to an objectto be removed on a surface of which a conductive portion (metal film)and an insulating portion are mixed, such as a printed board, forexample. In the case of an object to be removed on which minute metalfilms are provided partially, such as a printed board, it is difficultto make the first electrode 13 and the second electrode 14 opposed tothe same metal film, which results in the necessity of applying a highvoltage. Further, on a printed board, metal films often are provided atlower positions than the position of an insulating portion, and thus itis impossible to move the electrodes 13 and 14 while the electrodes 13and 14 are in contact with the metal films. Accordingly, for continuousdischarging, a gap is required between the metal films and theelectrodes 13 and 14. For these reasons, the removal efficiency isreduced. To solve these problems, in the case of an object to be removedon a surface of which a conductive portion and an insulating portion aremixed, as in the present embodiment, the conductivity on the surface ismeasured so as to determine the necessity of preliminary discharging,and if determined necessary, preliminary discharging is performedfollowed by a removal operation. Consequently, discharging can beperformed while a necessary gap is maintained and without increasing avoltage, resulting in an increase in removal efficiency.

Hereinafter, an exemplary processing operation of the metal coatingremoving apparatus of the present embodiment will be describedspecifically with reference to FIGS. 27 and 28. FIG. 27 is a blockdiagram of the metal coating removing apparatus of the presentembodiment, and FIG. 28 is a flow chart showing the operation of thismetal coating removing apparatus. The following description is directedto the case of an object to be removed on a surface of which aconductive portion and an insulating portion are mixed.

When an image recognition device 17 confirms the object to be removed, acontrol unit 16 recognizes the shape of the object to be removed, whichis performed in the same manner as for the metal coating removingapparatuses 1 to 4 in Embodiments 1 to 4 (S41 and S42). However,according to the present configuration, the necessity of preliminarydischarging is determined next, and if determined necessary, preliminarydischarging is performed.

Initially, the metal coating removing apparatus lowers, for example, aprobe (not shown) for measuring a film thickness connected with the filmthickness measuring device 19 and a conductivity measuring device 51 byusing a motor or the like, for example, so as to measure theconductivity on a surface layer of the object to be removed and the filmthickness thereof (S281). Then, the necessity of preliminary dischargingis determined based on whether the conductivity is exhibited or not(S282). If preliminary discharging is determined to be necessary,preliminary discharging is performed (S283). Preliminary discharging isperformed in S283 in the same manner as that described in Embodiment 4,and a detailed description thereof will be omitted here.

After preliminary discharging or after the determination thatpreliminary discharging is unnecessary, a removal operation isperformed. The removal operation is performed in the same manner as inS102 to S104 of the metal coating removing apparatus 2 described inEmbodiment 2 and in S50 to S56 of the metal coating removing apparatus 1described in Embodiment 1, and a description thereof will be omittedhere.

In the present embodiment, the same electrode configuration as that inEmbodiment 4 also may be used to perform preliminary discharging and theremoval operation.

Embodiment 6

In the present embodiment, other examples of the first electrode 13 andthe second electrode 14 in the metal coating removing apparatusdescribed in each of Embodiments 1 to 5 will be described with referenceto FIGS. 29 to 31.

As shown in FIG. 29, an insulating cover 15 for each of the firstelectrode 13 and the second electrode 14 may be provided only at a frontend portion thereof Further, as shown in FIG. 30A, instead of theinsulating covers 15, an insulating cap 61 may be provided so as tocover the front end portions of the first electrode 13 and the secondelectrode 14. FIG. 30B is a cross sectional view taken along a line I-Iin FIG. 30A. When the first electrode 13 and the second electrode 14 areopposed to an object to be removed, the insulating cap 61 can cover apart of the object to be removed opposed to the first electrode 13 andthe second electrode 14, resulting in an increase in removal efficiency.

As shown in FIGS. 31A and 31B, an insulating member 62 may be providedbetween the first electrode 13 and the second electrode 14, anddischarging is performed so as to remove a metal coating 101. With thisconfiguration, the insulating member 62 limits (narrows) a dischargespace, and therefore the metal coating 101 can be removed efficiently.FIG. 31A is a perspective view of the electrodes during a removaloperation, and FIG. 31B is a partially cross-sectional side viewcorresponding to FIG. 31A.

The apparatus and the method for removing a metal coating according tothe present invention will be described more specifically by way ofexamples.

EXAMPLE 1

In Example 1, a sample 1-a of a metal coating removing apparatus wascreated so that the first electrode 13 and the second electrode 14, eachbeing provided with the insulating cover 15, were positioned withrespect to the metal coating 101 as shown in FIG. 32. The firstelectrode 13 and the second electrode 14 were formed of tungsten and hada rod shape (diameter: 0.5 mm). The insulating cover 15 was formed ofaluminum oxide and had a tube shape with an outer diameter of 2.0 mm andan inner diameter of 1.0 mm so as to cover each of the electrodes 13 and14. An electrode-to-electrode distance d1 was 4 mm, anelectrode-to-object to be removed distance d2 was 0.2 mm, and an angle θof the electrodes with respect to the object to be removed was 45degrees. The direct current power source of the pulse power generator 11had a voltage of 15 kV, and the capacitor had a capacity of 400 nF.Further, a sample 1-b also was created that has the same configurationas that of the sample 1-a except that the insulating cover 15 was notprovided.

By using the samples 1-a and 1-b thus created, the metal coating 101provided on a surface of the resin 102 was removed. An ABS(acylonitrile-butadiene-styrene) resin plate (thickness: 2 mm) was usedas the resin 102, and a nickel-chromium plating film having a thicknessof 30 μm and a base metal of copper was used as the metal coating 101.FIG. 33 shows the removal area per 1 pulse in each of the case where themetal coating 101 was removed by using the sample 1-a (with theinsulating covers) and the case where the metal coating 101 was removedby using the sample 1-b (with no insulating cover). From these results,it was confirmed that the electrodes covered with the insulating coversallowed a larger removal area to be obtained with an identical appliedvoltage.

EXAMPLE 2

In Example 2, samples of the metal coating removing apparatus (sample1-a with the insulating covers) created in Example 1 were created sothat an electrode-to-electrode distance d1, an electrode-to-object to beremoved distance d2, and a direct current voltage (applied voltage) werevaried. The electrode-to-electrode distance d1 was 3 mm, 4 mm, 5 mm, or6 mm. The electrode-to-object to be removed distance d2 was 0 mm, 0.1mm, 0.5 mm, 1.0 mm, or 2.0 mm. The direct current power source was 5 kV,10 kV, or 15 kV. The removal by each of the samples was evaluated asshown in Table 2. In Table 2, the evaluation of the removal is expressedas follows: by using ⊚(d1: 4 mm, d2: 0.1 mm, applied voltage: 5 kV) asthe reference (removal area: 100%), ∘ represents that a removal area ofalmost 100% (about 80% to 100%) was obtained, Δ represents that aremoval area of about 80% or lower was obtained, ▴ represents that aremoval area of 40% or lower was obtained, and x represents thatdischarging hardly occurred.

TABLE 2 Electrode-to-object Electrode-to-electrode to be removed Applieddistance d1 distance d2 voltage 3 mm 4 mm 5 mm 6 mm   0 mm  5 kV ▴ ▴ ▴ ▴10 kV Δ Δ Δ Δ 15 kV ∘ ∘ ∘ ∘ 0.1 mm  5 kV ▴ ▴ ▴ ▴ 10 kV Δ Δ Δ Δ 15 kV ∘ ⊚∘ ∘ 0.5 mm  5 kV ▴ ▴ ▴ ▴ 10 kV Δ Δ Δ Δ 15 kV Δ Δ Δ Δ 1.0 mm  5 kV ▴ ▴ ▴▴ 10 kV Δ Δ Δ Δ 15 kV Δ Δ Δ Δ 2.0 mm  5 kV X X X X 10 kV ▴ ▴ Δ Δ 15 kV ▴▴ Δ Δ

According to the results shown in Table 2, when the electrode-to-objectto be removed distance d2 was 1.0 mm or lower, the result was ▴ when thedirect current power source had a voltage of 5 kV, and was Δ when thedirect current power source had a voltage of 10 kV, with respect to anelectrode-to-electrode distance d1 of 3 to 6 mm. Further, when thevoltage was 15 kV, the result was ∘ with respect to anelectrode-to-object to be removed distance d2 of 0 mm and 0.1 mm, andwas Δ with respect to an electrode-to-object to be removed distance d2of 0.5 mm and 1.0 mm. When the electrode-to-object to be removeddistance d2 was comparatively large (herein, 2.0 mm), relativelypreferable results were obtained with respect to anelectrode-to-electrode distance d1 of 5 mm or more. The reason for thisis considered as follows: a large electrode-to-object to be removeddistance d2 and a small electrode-to-electrode distance d1 allow acurrent to flow between the first electrode 13 and the second electrode14, which makes it difficult to remove the metal coating 101, andtherefore a certain distance is required between the electrodes. It wasconfirmed that the electrode-to-object to be removed distance d2 waspreferably 1.0 mm or lower. However, when the electrode-to-object to beremoved distance d2 was 0 mm, a surface of the resin 102 was burned.This proved that in order to recycle resins, preferably, discharging isperformed without bringing the electrodes into contact with the metalcoating 101 (by setting d2 to 0.1 mm or more).

EXAMPLE 3

In Example 3, the metal coating 101 provided on a surface of the resin102, the metal coating 101 being provided with an insulating film on itssurface as a protective film, was removed by using the metal coatingremoving apparatus 4 described in Embodiment 4. An ABS resin plate(thickness: 1.2 mm) was used as the resin 102, an Al film having athickness of 50 nm was used as the metal coating 101, and an ultravioletcurable resin film having a thickness of 20 μm was used as theinsulating film. The first electrode 13 and the second electrode 14 wereformed of the same material as in Example 1. With the metal coatingremoving apparatus 4 thus configured, the removal efficiency in thecases where an electrode-to-object to be removed distance (gap) was 3 mmand 0 mm, respectively, with respect to an electrode-to-electrodedistance of 2 mm was obtained by changing the applied voltage. When agap of 3 mm was provided, the removal efficiency in each of the caseswhere preliminary discharging was performed (plasma was generatedbetween the electrodes) and where preliminary discharging was notperformed was obtained. When a gap of 0 mm was provided, the removalefficiency only in the case where preliminary discharging was notperformed was obtained. The removal efficiency was obtained by measuringa removal area per 1 joule. The applied voltage during preliminarydischarging was the same as that used for the removal. The results areshown in FIG. 34. By performing preliminary discharging so as togenerate plasma between the electrodes, even when a gap of 3 mm wasprovided, the removal efficiency was as high as that obtained when nogap was provided. In the case where a gap of 3 mm was provided andpreliminary discharging was not performed, the removal area per 1 pulsewas almost 0 mm² even by increasing the applied voltage.

According to the above results, it was confirmed that in the case of ametal coating with an insulating film provided on its surface, theremoval efficiency was increased by removing the metal coating aftergenerating plasma between the electrodes by preliminary discharging.

EXAMPLE 4

In Example 4, the metal coating 101 provided on the resin 102 wasremoved by using the metal coating removing apparatus 4 described inEmbodiment 4. In the present example, a laminate of a Cu film (20 μm),an Ni film (10 μm), and Cr (0.2 μm) that is provided on an ABS resinplate was used as an object to be removed. The removal efficiency withrespect to an applied voltage of 3 kV, 5 kV, 10 kV, and 15 kV wasobtained by changing an electrode-to-object to be removed distance(gap). The removal efficiency was obtained by measuring a removal areaper 1 pulse. Only when the applied voltage was 3 kV, the removalefficiency in each of the cases where preliminary discharging wasperformed and where preliminary discharging was not performed wasobtained. When the other voltages were applied, the removal efficiencyonly in the case where preliminary discharging was not performed wasobtained. The applied voltage during preliminary discharging was 3 kV.The results are shown in FIG. 35. As can be seen from the results, whenpreliminary discharging was not performed, the removal efficiencydecreased with an increase of the gap, which raised the need to increasethe applied voltage. However, even when a high voltage was applied, theremoval area per 1 pulse was small. On the other hand, when preliminarydischarging was performed, the removal area per 1 pulse was largeregardless of the size of the gap, which proved that the metal coatingwas removed efficiently.

Further, with respect to a printed board in which a laminated film of Cu(35 μm)/Ni (5 μm)/Cr (0.1 μm) was provided on a resin board as aninsulating portion, a removal operation was performed after performingpreliminary discharging. As a result, the insulating portion was removedmore efficiently than in the case where preliminary discharging was notperformed.

EXAMPLE 5

In Example 5, a thermal plasma generating state between the electrodesby preliminary discharging was obtained. A pulse discharge circuit ofthe pulse power generator 11 used herein included a primary side circuitand a secondary side circuit as shown in FIG. 5. In the present example,it was confirmed whether or not thermal plasma was generated between theelectrodes by changing the output voltage of the secondary side circuit,the electrode material, and the discharge frequency. The results areshown in Table 3. As shown in Table 3, in each of the cases wheretungsten, copper-tungsten, silver-tungsten, and copper were used as theelectrode material, it was confirmed that thermal plasma was generatedby selecting the output voltage of the secondary side circuit or thedischarge frequency.

TABLE 3 Thermal Secondary plasma Electrode side output Dischargegenerating material voltage frequency state Ex. 1 Tungsten 3 kV 2 Hz ◯Ex. 2 Tungsten 3 kV 6 Hz ◯ Ex. 3 Tungsten 3 kV 20 Hz  ◯ Ex. 4 Tungsten 3kV 50 Hz  ◯ Ex. 5 Copper-tungsten 3 kV 5 Hz ◯ Ex. 6 Copper-tungsten 3 kV2 Hz X Ex. 7 Copper-tungsten 3 kV 3 Hz ◯ Ex. 8 Copper-tungsten 3 kV 20Hz  ◯ Ex. 9 Silver-tungsten 3 kV 1 Hz X Ex. 10 Silver-tungsten 3 kV 3 Hz◯ Ex. 11 Silver-tungsten 3 kV 5 Hz ◯ Ex. 12 Silver-tungsten 3 kV 50 Hz ◯ Ex. 13 Copper 3 kV 5 Hz ◯ Ex. 14 Copper 3 kV 1 Hz X Ex. 15 Copper 3 kV3 Hz X Ex. 16 Copper 3 kV 50 Hz  ◯ Ex. 17 Tungsten 15 kV  3 Hz X Ex. 18Tungsten 15 kV  5 Hz ◯ Ex. 19 Tungsten 15 kV  50 Hz  ◯ Ex. 20Silver-tungsten 15 kV  5 Hz X Ex. 21 Silver-tungsten 15 kV  6 Hz ◯ Ex.22 Silver-tungsten 15 kV  50 Hz  ◯ Ex. 23 Copper-tungsten 15 kV  3 Hz XEx. 24 Copper-tungsten 15 kV  5 Hz X Ex. 25 Copper-tungsten 15 kV  6 Hz◯ Ex. 26 Copper-tungsten 15 kV  50 Hz  ◯

INDUSTRIAL APPLICABILITY

The apparatus and the method for removing a metal coating according tothe present invention can be used to remove a metal coating provided ona surface of a resin, and particularly can be applied effectively to theremoval of a metal coating with a view to recycling resins.

1. A metal coating removing apparatus for removing a metal coatingprovided on a surface of a resin, comprising: a first electrode arrangedso as to be opposed to the metal coating provided on the surface of theresin; a second electrode arranged so as to be opposed to the metalcoating at a predetermined distance from the first electrode; and adischarge energy supply portion for supplying discharge energy betweenthe first electrode and the second electrode so as to allow dischargingto occur between the first electrode and the second electrode, therebyremoving the metal coating, wherein at least one of the first electrodeand the second electrode is covered with an insulating cover made of aninsulating material except for at least a portion opposed to the metalcoating provided on the surface of the resin, and the insulating coverand the at least one electrode covered with the insulating cover areprovided so that relative positions of the insulating cover and theelectrode are adjustable.
 2. The metal coating removing apparatusaccording to claim 1, further comprising an insulating member arrangedbetween the first electrode and the second electrode.
 3. The metalcoating removing apparatus according to claim 1, further comprising aninsulating cap for covering at least front end portions of the firstelectrode and the second electrode.
 4. The metal coating removingapparatus according to claim 1, wherein the insulating cover is providedso that one end of the insulating cover contacts with the object to beremoved during a removal operation, and the at least one electrodecovered with the insulating cover is provided so as to be kept fromcontact with the metal to be removed during the removal operation. 5.The metal coating removing apparatus according to claim 1, furthercomprising an output control portion for controlling the dischargeenergy supply portion, wherein the output control portion controls atleast either one of an amount of the discharge energy and a dischargefrequency supplied from the discharge energy supply portion.
 6. Themetal coating removing apparatus according to claim 1, furthercomprising an electrode-to-electrode distance control portion forcontrolling a distance between the first electrode and the secondelectrode.
 7. The metal coating removing apparatus according to claim 1,further comprising an electrode-to object to be removed distance controlportion for controlling a distance between the first electrode as wellas the second electrode and the object to be removed.
 8. The metalcoating removing apparatus according to claim 1, further comprising anelectrode angle control portion for controlling an angle of the firstelectrode and the second electrode with respect to the object to beremoved in a range of 0 to 90 degrees.
 9. The metal coating removingapparatus according to claim 1, further comprising an image recognitionportion for recognizing a shape of the object to be removed.
 10. Themetal coating removing apparatus according to claim 1, furthercomprising a film thickness measurement portion for measuring athickness of the object to be removed.
 11. The metal coating removingapparatus according to claim 1, further comprising a metal recognitionportion for recognizing a type of a metal of the object to be removed.12. The metal coating removing apparatus according to claim 1, wherein adistance between the first electrode and the second electrode is notless than 1 mm and not more than 20 mm.
 13. The metal coating removingapparatus according to claim 1, wherein a distance between the firstelectrode as well as the second electrode and the object to be removedis not less than
 01. mm and not more than 3.0 mm.
 14. The metal coatingremoving apparatus according to claim 1, wherein an angle of the firstelectrode and the second electrode with respect to the object to beremoved is not less than 15 degrees and not more than 90 degrees. 15.The metal coating removing apparatus according to claim 1, furthercomprising a plasma generation portion for generating plasma between thefirst electrode and the second electrode.
 16. The metal coating removingapparatus according to claim 15, wherein the plasma generation portionsupplies discharge energy between the first electrode and the secondelectrode so as to allow discharging to occur between the firstelectrode and the second electrode, thereby generating plasma.
 17. Themetal coating removing apparatus according to claim 16, wherein theplasma generation portion allows discharging to occur between the firstelectrode and the second electrode in the vicinity of a conductivematerial, thereby generating plasma between the first electrode and thesecond electrode.
 18. A metal coating removing method for removing ametal coating provided on a surface of a resin, comprising: arranging afirst electrode and a second electrode so that they are opposed to themetal coating provided on the surface of the resin; and supplyingdischarge energy between the first electrode and the second electrode soas to allow discharging to occur between the first electrode and thesecond electrode, thereby removing the metal coating, at least one ofthe first electrode and the second electrode being covered with aninsulating cover made of an insulating material except for at least aportion opposed to the metal coating provided on the surface of theresin, and the insulating cover and the at least one electrode coveredwith the insulating cover being provided so that relative positions ofthe insulating cover and the electrode are adjustable.
 19. The metalcoating removing method according to claim 18, comprising controlling atleast either one of an amount of the discharge energy and a dischargefrequency in accordance with at least either one of a thickness and atype of a metal of the object to be removed.
 20. The metal coatingremoving method according to claim 18, comprising controlling a distancebetween the first electrode and the second electrode in accordance withat least either one of a thickness and a type of a metal of the objectto be removed.
 21. The metal coating removing method according to claim18, comprising controlling a distance between the first electrode aswell as the second electrode and the object to be removed in accordancewith at least either one of a thickness and a type of a metal of theobject to be removed.
 22. The metal coating removing method according toclaim 18, comprising controlling an angle of the first electrode and thesecond electrode with respect to the object to be removed in accordancewith at least either one of a thickness and a type of a metal of theobject to be removed.
 23. The metal coating removing method according toclaim 18, comprising: subjecting the object to be removed to testremoval ahead of time; measuring a removal area obtained by the testremoval; and controlling at least either one of an amount of thedischarge energy and a discharge frequency in accordance with a resultof measuring the removal area.
 24. The metal coating removing methodaccording to claim 18, comprising generating plasma between the firstelectrode and the second electrode before arranging the first electrodeand the second electrode so that they are opposed to the metal coatingprovided on the surface of the resin.
 25. The metal coating removingmethod according to claim 24, comprising supplying discharge energybetween the first electrode and the second electrode so as to allowpreliminary discharging to occur between the first electrode and thesecond electrode, thereby generating plasma between the first electrodeand the second electrode, before arranging the first electrode and thesecond electrode so that they are opposed to the metal coating providedon the surface of the resin.
 26. The metal coating removing methodaccording to claim 25, wherein the preliminary discharging is performedin a state where the first electrode and the second electrode arearranged in the vicinity of a conductive material.